Human oocyte cryopreservation: 5-year experience with a sodium-depleted slow freezing method

Abstract

A slow freezing/rapid thawing method for the cryopreservation of human oocytes has been employed using a sodium-depleted culture media. In 53 frozen egg-embryo transfer (FEET) cycles, a 60.4% survival rate post-thaw was obtained and a 62.0% fertilization rate following intracytoplasmic sperm injection. Overall pregnancy rates were 26.4% per thaw attempt, 30.4% per patient, and 32.6% per embryo transfer. Pregnancy rates using sodium-depleted phosphate-buffered saline (PBS) as the base medium were 20.0% per thaw, 21.7% per patient, and 26.3% per transfer. With sodium-depleted modified human tubal fluid (mHTF) as the base for the cryopreservation medium, rates were 32.1% per thaw attempt, 39.1% per patient, 37.5% per transfer. The overall implantation rates were 4.2% per thawed oocyte and 13.6% per embryo, (PBS: 3.0% per egg, 10.6% per embryo; mHTF:5.3% per oocyte; 15.9% per embryo). These data indicate that the use of a sodium-depleted media with slow freezing and rapid thawing can yield acceptable pregnancy rates after FEET.

Live birth following transfer of a cryopreserved embryo generated from a cryopreserved oocyte and a cryopreserved sperm: Case report

“…The number of babies born following in vitro fertilization of cryopreserved oocytes has steadily increased over the last few years [5][6][7][8][9][10]. Much of this growth can be attributed to changes in the law in Italy, which resulted in the prohibition of embryo cryopreservation.…”

“…The resurgence of interest in human oocyte cryopreservation as a consequence of a number of reports suggesting that it may be a safe option in appropriate circumstances [1][2][3][4] has led to its clinical application and reports of a number of live births [5][6][7][8][9][10]. Although this approach has been adopted as an adjunct to routine IVF practice in Italy, this is predominantly a consequence of legal developments which resulted in the prohibition of the alternative, and more widepread, option of embryo cryopreservation.…”

Human oocyte and ovarian tissue cryopreservation and its application

“…This change halts the sperm penetration of zona and inhibits embryonic hatching, but these problems can be overcome by intracytoplasmic sperm injection and assisted hatching [27][28][29]. Several studies, however, have recently reported better post-thaw oocyte survival, fertilization, and pregnancy rates [30,31]. The incidence of chromosomal abnormalities in human embryos obtained from cryopreserved oocytes was no different from that of control embryos [32].…”

“…One main technique is slow freezing. Slow freezing gives acceptable results for human oocyte recently [30,31,64,65]. A major problem during the procedure of slow freezing is the time of exposure of oocyte to the cryoprotectants.…”

Maturation outcomes are improved following Cryoleaf vitrification of immature human oocytes when compared to choline-based slow-freezing

“…Past clinical studies with GV oocytes from a variety of sources as well as freezing protocols have documented wide ranges for survival, maturation, fertilization, and pre-implantation development (slow-freezing: [7][8][9][10][11][12]; vitrification: [13][14][15][16]). For mature oocytes, advancements in protocols have resulted in encouraging outcomes, including slow-freezing with choline-substitution [17][18][19][20] and vitrification with the Cryoleaf system [15,[21][22][23][24]. However, there are limited prior reports of either cholinebased slow-freezing [11,25] or vitrification with the Cryoleaf [15] in human GV oocytes, with no previous assessments of spindle integrity or chromosome alignment.…”